Modern diesel engines are often equipped with multiple pressure sensors and one or more turbochargers. Pressure sensors send ambient pressure, intake manifold pressure and other important pressure readings to an engine Electronic Control Module (ECM). These pressure readings are inputs for many engine control algorithms. When one of the pressure sensors stops measuring correctly, a diagnostic method has to detect the malfunction immediately in order to avoid engine system failure. While it is easy for a diagnostic algorithm to detect a difference among pressure sensors, it is a challenging task to accurately identify which pressure sensor is faulty, particularly when there are only two correlated sensors or all pressure sensors show a small deviation from a nominal value. An additional reference sensor added as a redundant sensor allows voting but increases engine cost and introduces another point of failure.
US Publication 20080066522 (the '522 publication) to Thiel discloses a method for determining the operability of a pressure sensor. The '522 publication utilizes a reference pressure sensor that is not an operating element of the internal combustion engine to provide a reference ambient pressure. All engine onboard sensors read ambient pressure values and compare to the reference ambient pressure value determined by the reference pressure sensor.
The '522 publication assumes that the reference pressure sensor itself is working perfectly and the reference pressure is calibrated by external pressure calibration system. The reference pressure sensor does not provide useful input for the ECM control algorithm and when engine operates correctly, the reference pressure sensor is redundant. In order to ensure correct operation of the reference pressure sensor, frequent calibration has to be performed. It is costly and time consuming to calibrate any pressure sensor as the calibration requires a special environment including pressure gauges.